Download Inheritance Ch12

Inheritance Patterns:
Determined by Chromosome
Movements in Meiosis
• 1st Illustration:
Down Syndrome
– Trisomy 21, or Down Syndrome)
(F12.19 p. 232)
• Nondisjunction at Meiosis I
• Down syndrome frequency increases with maternal
age
(F12.20 p. 233)
– One of Many Caused by Abnormal Numbers of
Autosomes
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Inheritance Patterns:
Determined by Chromosome
Movements in Meiosis
• 2nd Illustration: Sex Determination
– Human sex chromosomes
– Sex determination in mammals
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(F12.8 p. 219)
(F12.9 p. 219)
Y chromosome
X chromosome
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female parent
X1
X2
eggs
X1
X1
male parent
Y
Xm
X2
Xm
Xm
sperm
Xm
X2
female offspring
X1
Y
X2
Y
male offspring
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Y
Inheritance Patterns:
Determined by Chromosome
Movements in Meiosis
• Some Genetic Disorders Are Caused by
Abnormal Numbers of Sex Chromosomes
– Effects of Nondisjunction of the Sex
Chromosomes During Meiosis
•
•
•
•
(T12.2 p. 230)
Turner Syndrome (XO)
Trisomy X (XXX)
Klinefelter Syndrome (XXY)
XYY Males
– Medicinal plants
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(FE12.2 p. 231)
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Inheritance of Single Genes
• Illustration 1:
Sex-Linked Genes
– Found Only on the X or Only on the Y
Chromosome
• Sex-linked: eye color in fruit flies
(F12.10 p. 220)
• Some Sex-Linked Human Genetic Disorders
– Color blindness, a sex-linked recessive trait
– Hemophilia among the royal families of Europe
– Dominant & Recessive Alleles
– Homozygous & Heterozygous Individuals
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(F12.17 p. 228)
(F12.18 p. 229)
female parent
r
R
XRXr
XR Xr
R
r
eggs
XR
R
Xr
R
R
r
R
all the F2
females
have red eyes
male parent
XRY
XR
sperm
R
XR Y
Y
XR XR
female offspring
R
half the F2
males
have red eyes,
half have white
eyes
r
XRY
male offspring
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Xr XR
Xr Y
Inheritance of Single Genes
• 12.8.2 Some Human Genetic Disorders
Are Caused by Dominant Alleles
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I
maternal
grandfather
II
mother
aunts
father
III
sister
?
IV
G. Audesirk
T. Audesirk
?
daughter
or
= colorblind
= heterozygous carrier female,
normal color vision
or
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= normal color vision (not carrier)
Edward
Duke of Kent
Albert
Prince
of SaxeCoburg-Gotha
Edward VII
King of
England
unaffected male
hemophiliac male
unaffected female
carrier female
Victoria
Princess of
Saxe-Coburg
Victoria
Queen
of England
Alexandra
of Denmark
Leopold
Duke
of Albany
Helen
Louis IV
Princess of
Grand Duke of
Waldeck-Pyrmont Hesse-Darmstadt
Alice
Princess
of Hesse
several
unaffected
chidren
Beatrice
Henry
Prince of
Battenburg
present British
royal family
(unaffected)
Victoria Elizabeth Alexandra
Mary
Tsarina
carrier
daughter
and
hemophiliac
grandson
Nicholas II Frederick Ernest Mary Irene
Victoria
of Russia
?
?
?
?
Olga
Tatiana
Maria
Anastasia
Alexander Alfonso
Albert
XII
Victoria Leopold Maurice
Queen
of Spain
?
Alexis
Tsarevitch
Alfonso
Crown
Prince
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2004
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Juan
Beatrice
?
died Marie Jaime Gonzalo
in
infancy
Inheritance of Single Genes
Explained by Mendel’s Laws
• Gregor Mendel
(F12.1 p. 210)
• The relationships among genes, alleles,
and chromosomes
(F12.2 p. 210)
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chromosome 1
from tomato
pair of
homologous
chromosomes
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Gregor Mendel: Laid the
Foundation for Modern Genetics
• Doing It Right: The Secrets of Mendel’s Success
–
–
–
–
–
–
–
–
Flowers of the edible pea
(F12.3 p. 211)
1st generation offspring of the flowering pea
F1
(F1 p. 211)
2nd generation offspring of the flowering pea
F2 (F 2 p. 212)
Homozygous parent
P = Parental (F 3 p. 212)
Heterozygous parent
(F 4 p. 212)
Homozygous allele distribution
(F 5 p. 213)
Heterozygous 1st generation offspring allele distribution (F6 p. 213)
Heterozygous 2nd generation offspring allele distribution (F7 p. 213)
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intact pea flower
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flower dissected to show
reproductive structures
pollen
Parental
generation (P)
pollen
cross-fertilize
true-breeding,
purple-flowered
plant
true-breeding,
white-flowered
plant
First-generation
offspring (F1)
all purple-flowered
plants
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Firstgeneration
offspring (F1)
self-fertilize
Secondgeneration
offspring (F2)
3/4 purple
1/4 white
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Inheritance of Single Traits
• Mendel’s Law of RANDOM SEGREGATION
– THE 2 ALLELES OF A GENE “SEGREGATE” TO DIFFERENT
GAMETES
– Explains the Results of Mendel’s Crosses
– Predicts the Outcome of New Types of Single-Trait Crosses
– Inheritance of Dominant & Recessive Alleles on Homologous
Chromosomes
• Determines the outcome of a single-trait cross
(F12.4 p. 214)
– Test cross
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(F8 p. 215)
homozygous parent
A
A
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gametes
A
A
purple parent
P
PP
P
all P sperm and eggs
white parent
pp
p
p
all p sperm and eggs
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heterozygous parent
A
a
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gametes
A
a
F1
offspring
sperm
eggs
P
p
Pp
P
Pp
or
p
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gametes from
F1 plants
eggs
sperm
F2
offspring
P
P
PP
P
p
Pp
p
P
Pp
p
p
pp
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Pp
self-fertilize
1
2
P
eggs
1
2
p
sperm
1 P
2
1
4
PP
1
4
Pp
1
4
pP
1
4
pp
1
p
2
sperm
eggs
offspring
genotypes
1 P
2
1
2
P
1
4
PP
1
P
2
1
2
p
1
4
Pp
genotypic
ratio
(1:2:1)
1
PP
4
2
4 Pp
1
2
P
1
2
P
1
4
pP
1
2 P
1
2
p
1
4
pp
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phenotypic
ratio
(3:1)
1
4 pp
3
purple
4
1
white
4
pollen
PP or Pp
sperm unknown
pp
all eggs p
if PP
if Pp
p
egg
all
sperm P
p
all Pp
sperm
1
P
2
1 Pp
2
1
p
2
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1
2 pp
egg
Inheritance of Single Traits:
Multiple Traits on Different Chromosomes
• Mendel’s Law of INDEPENDENT ASSORTMENT
– GENES ON DIFFERENT CHROMOSOMES ARE INHERITED
INDEPENDENTLY
– Traits of pea plants that Mendel studied
(F12.5 p. 215)
– Predicting genotypes and phenotypes for a cross between gametes that are
heterozygous for two traits
(F12.6 p. 216)
– Independent assortment of alleles
(F12.7 p. 217)
– Heterozygous pea plant chromosomes
(F9 p. 217)
– Sweet pea at meiosis I
(F10 p. 218)
– Crossing over
(F11 p. 218)
– Sweet pea at anaphase I
F12(p. 218)
– Sweet pea at meiosis II
(F13 p. 218)
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Trait
Dominant form
Recessive form
Seed
shape
smooth
wrinkled
Seed
color
yellow
green
inflated
constricted
green
yellow
purple
white
Pod
shape
Pod
color
Flower
color
Flower
location at leaf
junctions
Plant
size
tall
(1.8 to
2 meters)
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at tips of
branches
dwarf
(0.2 to 0.4
meters)
SsYy
self-fertilize
eggs
1
4
sperm
1
4 SY
1
4 Sy
1
4 sY
1
sy
4
1
4
SY
1
4
1
sY
4
Sy
sy
1
16
SSYY
1
16
SSYy
1
16
SsYY
1
16
SsYy
1
16
SSyY
1
16
SSyy
1
16
SsyY
1
16
Ssyy
1
16
sSYY
1
16
sSYy
1
16
ssYY
1
16
ssYy
1
16
sSyY
1
16
sSyy
1
16
ssyY
1
16
ssyy
3
4
smooth x
3
4
yellow
phenotypic ratio
(9:3:3:1)
9
= 16 smooth yellow
3
4
smooth x
1
4
green
=
3
16
smooth green
1
4
wrinkled x
3
4
yellow
=
3
16
wrinkled yellow
1
4
wrinkled x
1
4
green
=
1
16
wrinkled green
seed shape
seed color
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S
pairs of alleles on homologous
chromosomes in diploid cells
s
Y
y
S
Y
s
y
chromosomes
replicate
replicated homologues
pair during metaphase
S
of meiosis I,
orienting like this
or like this
s
y
Y
meiosis I
S
Y
s
y
S
y
s
Y
S
Y
s
y
S
y
s
Y
meiosis II
S
S
Y
s
Y
S
s
y
y
S
y
s
y
s
Y
SY
sy
Sy
produces four equally
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Prentice Hall,assortment
Inc.
likely allele combinations during meiosis
Y
sY
12.4 How Are Genes
Located on the Same
Chromosome Inherited?
• 12.4.1 Genes on the Same
Chromosome Tend to Be Inherited
Together
• 12.4.2 Recombination Can Create
New Combinations of Linked Alleles
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flower color gene
pollen shape gene
purple
allele, P
long
allele, L
red
allele, p
round
allele, l
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flower color gene
pollen shape gene
sister
chromatids
purple allele, P
long allele, L
sister
chromatids
red allele, p
round allele, l
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homologous
chromosomes
(duplicated)
at meiosis I
crossing
over
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recombined
chromatids
P
L
p
L
P
l
p
l
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P
L
p
L
P
l
p
l
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12.6 Do the Mendelian Rules
of Inheritance Apply to All
Traits?
• 12.6.1 Incomplete Dominance: The
Phenotype of Heterozygotes Is
Intermediate Between the
Phenotypes of the Homozygotes
– Figure 12.11 Incomplete dominance
(p. 221)
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P:
RR
RR
RR
RR
F1:
F2:
1
2
R
1
4
1
4
1
2
R
RR
1
4
RR’
RR
1
4
R’R
eggs
R
sperm
1
2
1
2
R
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12.6 Do the Mendelian Rules
of Inheritance Apply to All
Traits?
• 12.6.2 A Single Gene May Have
Multiple Alleles
– Table 12.1 Human Blood Group
Characteristics (p. 222)
– Figure E12.1 Cystic fibrosis (p. 223)
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12.6 Do the Mendelian Rules
of Inheritance Apply to All
Traits?
• 12.6.3 Many Traits Are Influenced
by Several Genes
– Figure 12.12 Polygenic inheritance of
grain color in wheat (p. 224)
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R1R1R2R2
eggs
R1R2
R1R2
R1R2
R1R2
sperm
R1R2
R1R1R2R2
R1R1R2R2
R1R1R2R2 
R1R1R2R2
R1R1R2R2
R1R1R2R2 
R1R1R2R2
R1R1R2R2
R1R1R2R2
R1R1R2R2
R1R1R2R2 
R1R1R2R2
R1R1R2R2
R1R1R1R2
R1R1R2R2
R1R1R2R2
R1R1R2R2
R1R2
R1R2
R1R2
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12.6 Do the Mendelian Rules
of Inheritance Apply to All
Traits?
• 12.6.4 Single Genes Typically Have
Multiple Effects on Phenotype
• 12.6.5 The Environment Influences
the Expression of Genes
– Figure 12.13 Environmental influence on
phenotype (p. 225)
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12.7 How Are Human
Genetic Disorders
Investigated?
• Figure 12.14 Family pedigrees (p.
226)
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A pedigree for a dominant trait
I
II
III
A pedigree for a recessive trait
I
II
?
?
?
?
III
?
IV
?
?
How to read pedigrees
I, II, III = generations
= male
= female
= parents
= offspring
or
= shows trait
or
= does not show trait
or
= known carrier (heterozygote) for
recessive trait
? or ? = cannot determine genotype from pedigree
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12.8 How Are Human
Disorders Caused by Single
Genes Inherited?
• 12.8.1 Some Human Genetic
Disorders Are Caused by Recessive
Alleles
– 12.8.1.1 Albinism Results from a Defect
in Melanin Production
• Figure 12.15 Albinism (p. 227)
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Human
Rattlesnake
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Wallaby
12.8 How Are Human
Disorders Caused by Single
Genes Inherited?
– 12.8.1.2 Sickle-Cell Anemia Is Caused by
a Defective Allele for Hemoglobin
Synthesis
• Figure 12.16 Sickle-cell anemia (p. 227)
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